Phase 2 core: ClaudeDriver over stream-json, permissions and questions on the phone

The second driver behind the same trait: claude -p with stream-json both
ways, the hidden --permission-prompt-tool stdio flag (without which no
permission ever reaches a client), text deltas streamed from raw API
events, tool_use/tool_result mapped to tool events, and can_use_tool
control requests surfaced as Question events -- plain permissions as
Allow/Deny, AskUserQuestion as one Question per sub-question with the
chosen labels sent back in updatedInput.answers keyed by question text
(wire shapes pinned by live probes against CLI 2.1.237, recorded in the
module doc). The CLI session id is persisted per session dir, so a
backend restart respawns with --resume and loses nothing. set_model
rides the control protocol and persists through the manager; the spawn
screen grows model/cwd/permission-mode fields.

Also: the dev CA now carries proper keyUsage/basicConstraints
extensions (strict verifiers reject it otherwise) -- regenerated and
re-pinned before any real phone has installed the app.

Verified: 20 unit tests + clippy clean; scripted end-to-end over the
HTTP API (AskUserQuestion round trip, Bash permission allow, streaming,
restart with --resume remembering earlier work, delete); and on the
emulator, a live haiku session asking Tea-or-coffee and acknowledging
the tapped answer.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017xn8nHw1tw1R6PtiY1eEtw

server/Cargo.lock

@@ -983,6 +983,16 @@ version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f8fadd59c855ef2080decdef8ff161eb6661b86933c9d82e5ba29dc602a55aba"
 
+[[package]]
+name = "signal-hook-registry"
+version = "1.4.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c4db69cba1110affc0e9f7bcd48bbf87b3f4fc7c61fc9155afd4c469eb3d6c1b"
+dependencies = [
+ "errno",
+ "libc",
+]
+
 [[package]]
 name = "slab"
 version = "0.4.12"
@@ -1097,6 +1107,7 @@ dependencies = [
  "libc",
  "mio",
  "pin-project-lite",
+ "signal-hook-registry",
  "socket2",
  "tokio-macros",
  "windows-sys 0.61.2",